8 Answers
8

This answer isn't as cut and dry as some people are making out. You can do a ubuntu-standard package install and use that as a server. You can use ubuntu-minimal as a server. You can take ubuntu-desktop and break it so it doesn't use X... Or even leave X there for administration (eww). You can change the kernel packages from -server to -generic to -rt etc. You can change the motd or even just upgrade from a version where the motd isn't as long as the new one (none of my servers have ever come out with all that guff -- probably because they're upgraded from older LTSes).

I guess the questions that all of us should be asking are: Why does it matter? What are you trying to learn? What difference does it make to you?

If you're trying to run something graphical, check for what you actually need (X, x11vnc, etc). If you're trying to check that there isn't a graphical interface, do the same!

Well, that's a more specific question: what does ksplice check to decide whether you can use the free desktop version. I would guess they check for the desktop vs server kernel build.
–
poolieApr 29 '11 at 5:41

It's possible to have a perfectly working desktop without the ubuntu-desktop package. That's just a metapackage to ensure a certain standard set of supporting applications such as control panels, Debian-specific things etc are installed along with your desktop. If you remove any of these then ubuntu-desktop will effectively be "removed" too but you'll still have a desktop. It'd be much better to check for the xserver-xorg-core package instead. Although, the existence of that package doesn't guarantee it's being used, there's no good reason to have it installed on a non-desktop machine.
–
thomasrutterApr 23 '12 at 6:27

Yes, the fact that there is no sharp line between desktop and server has been extensively discussed by most answers, including mine. But ubuntu-desktop is a reasonable test for whether you have Ubuntu desktop. If you install from the desktop CD/ISO, you will have this package.
–
poolieAug 5 '13 at 2:42

Ubuntu 10.10
Welcome to Ubuntu!
* Documentation: https://help.ubuntu.com/
System information as of Wed Nov 10 20:54:11 UTC 2010
System load: 0.07 Processes: 78
Usage of /: 30.4% of 14.76GB Users logged in: 1
Memory usage: 38% IP address for eth0: XXXXXXXX
Swap usage: 0%
Graph this data and manage this system at https://landscape.canonical.com/
---------------------------------------------------------------------
At the moment, only the core of the system is installed. To tune the
system to your needs, you can choose to install one or more
predefined collections of software by running the following
command:
sudo tasksel --section server

It is also worth mentioning that this file is easily editable by sudo, which is done very often, because it's the message that user sees when he logs via ssh.

This is mostly telling you whether landscape-client is installed. That may happen to be true on servers, but it's not really essentially connected to whether you're using the server OS or not.
–
poolieNov 11 '10 at 1:04

It is possible to load the desktop features to server, and to remove them from desktop. The root issue is what packages are part of server functionality, and will get the additional period of support and updates.

The best answer (IMHO) can be found in a Launchpad question (from 2008):

You must remember that there is no fundamental difference between the Desktop and Server editions.

It is highly likely however that your hosting provider has not got all the graphical pieces, such as GNOME on the top of the stack, because there is no need of them. The installed packages is what makes it a server.

You might be interested in ubuntu-maintenance-check script (link) that tells you the maintenance cycle of each package installed - those that have a longer period are server packages.

If the currently installed linux-image package contains the word "server" in it, then you're running Ubuntu server.

For example, the current latest kernel package for Ubuntu 10.10 desktop:

linux-image-2.6.35-22-generic

And server:

linux-image-2.6.35-22-server

For a more generic package that should be the same across different versions of Ubuntu, linux-image-generic is the default package for Ubuntu desktop and linux-image-server is the default for the server edition.